<?php

$var_1 = [1,2,3];
$var_2 = [1,2,3,5];
//$var_3 = [];
//$var_4 = [];
//$var_5 = [];
//$var_6 = [];
$var_7 = [1,5];

$result = call_user_func_array(
        'array_intersect',
        array_filter(
            array( $var_1,$var_2,$var_3,$var_4,$var_5,$var_6,$var_7 ),
            function($a){ return isset($a)  &&  is_array($a)  &&  !!count($a);}
        )
    );
    
print_r( $result);